With a conventional vertical filling and packaging machine, liquid, pasty, or solid content is put in a cylindrical film while forming a film in a cylindrical shape that is fed in a vertical direction, and an upper part and a lower part of the cylindrical film are heat-sealed, whereby an envelope-shaped packaging bag with content is manufactured.
In the vertical filling and packaging machine, there are cases where a cylindrical film is filled with liquid or pasty content (hereinafter referred to as one part filling), where a cylindrical film is filled with liquid content at the same time when solid content is injected into the cylindrical film (hereinafter referred to as two parts filling), or where only solid content is injected into a cylindrical film.
There are included a pillow type, a three-side seal type, a four-side seal type, a standing type, etc. in the forms of packaging bags to be manufactured. All of these types of bags are manufactured in a way such that the width center of a belt-like film extending in a vertical direction is folded to be formed in a cylindrical shape, both of the overlapped sides of this cylindrical film are heat-sealed in a longitudinal direction, and further, each upper part and each lower part of the cylindrical film is heat-sealed in a lateral direction. However, as for the pillow type, a seal part in the longitudinal direction (hereinafter referred to as a vertical seal part) is located in the center of the lateral direction of the packaging bag (refer to FIG. 1a). As for the three-side seal type, the vertical seal part is located only at one end in the lateral direction of the envelope-shaped packaging bag (refer to FIG. 1b). As for the four-side seal type and the standing type, the vertical seal part is located at both ends in the lateral direction of the envelope-shaped packaging bag (refer to FIG. 1c). In particular, as for the standing type, the bottom of the packaging bag is formed so that a four-side seal type packaging bag can be displayed upright.
Here, a conventional vertical filling and packaging machine will be described using an example of manufacturing the four-side seal type envelope-shaped packaging bag. FIG. 2 is a view showing the main part of a conventional vertical filling and packaging machine (four-side seal type).
As shown in FIG. 2, a sheet-like film is fed in a vertical direction, the width direction ends of the sheet-like film overlap with each other by bag-making guide 2, and thereby cylindrical film 1 is formed.
Under bag-making guide 2, arranged are plural vertical seal devices 3 that perform heat-sealing in a longitudinal direction with respect to each folding part and each overlapping part of cylindrically formed film 1.
Plural vertical seal devices 3 are arranged opposed to each other in a state of sandwiching the folding part and the overlapping part of cylindrical film 1 therebetween, and they can move in a direction away from each other and in a direction in contact with each other. These vertical seal devices 3 enable vertical seal part 1d to be formed at both sides of cylindrical film 1.
Above each vertical seal device 3, a pair of guide rollers 4 that rotate sandwiching the sides of cylindrical film 1 to feed cylindrical film 1 downwardly is provided.
Under vertical seal devices 3, a pair of ironing rollers 5 that are arranged opposed to each other sandwiching cylindrical film 1 therebetween, and that are rotated in synchronization with rotations of guide rollers 4 is provided. Ironing rollers 5 separate content injected into cylindrical film 1 by sandwiching the full width in the lateral direction of cylindrical film 1, and they can move in a direction away from each other and in a direction in contact with each other.
Under ironing rollers 5, a pair of lateral seal devices 6 that are arranged opposed to each other sandwiching cylindrical film 1 therebetween, and that form a heat seal part in the lateral direction (hereinafter referred to as lateral seal part 1e) over the full width of cylindrical film 1 is arranged.
Further, injection pipe 7 that injects a product in cylindrical film 1 extends in the vertical direction from an upper side of bag-making guide 2 to right above ironing rollers 5 through an inside of bag-making guide 2.
In the above-mentioned filling and packaging machine, vertical seal part 1d is formed at the both sides of cylindrical film 1, respectively by vertical seal devices 3, lateral seal part 1e is formed in the lateral direction of cylindrical film 1 by lateral seal devices 6, and a product is injected into cylindrical film 1 from injection pipe 7 in a state in which a space between ironing rollers 5 is opening. Subsequently, the space between ironing rollers 5 is closed, and content in cylindrical film 1 is separated in a film feeding direction by ironing rollers 5. When guide rollers 4 and ironing rollers 5 are rotated in this state to feed cylindrical film 1 downwardly, an empty portion without content is formed in cylindrical film 1.
When the empty portion is fed to lateral seal devices 6, the feeding of cylindrical film 1 is stopped, and opposed lateral seal devices 6 are moved closer to each other. As a result, the films sandwiched between lateral seal devices 6 are heat-welded to form a lateral seal part, and as a result, the upper opening of cylindrical film 1 is sealed. Subsequently, when the film is cut off at a portion of the lateral seal part, a four-side seal type envelope-shaped packaging bag with the product can be obtained.
It is to be noted that an exemplary mechanism of a conventional vertical filling and packaging machine is described also in the following Patent Documents 1 and 2.
Consideration is given to using the above-described vertical filling and packaging machine for a manufacturing apparatus for retort pouch food. High airtightness is required for packaging bags in the retort pouch food industry. For that reason, three-side seal type or four-side seal type packaging bags are desirably used instead of pillow type ones in the retort pouch food industry. Since the vertical seal part on the periphery of the bag in the pillow type packaging bag does not have an edge piece, the corners of the content filling portion of the bag easily touch the outside. As a result of this, such problems occur that the corners easily have pinholes, the sharp corners damage other bags, etc., and thus the three-side seal type or the four-side seal type packaging bags are desirably used.
However, there has been a case where the lateral seal part is wrinkled when manufacturing the three-side seal type or the four-side seal type packaging bag with content using the conventional vertical filling and packaging machine. This phenomenon has occurred even though a filling method of the content is the one part filling, the two parts filling, or the solid-only filling one. Such formation of wrinkles leads to poor appearance and reduction of airtightness of the bag. Accordingly, it has been necessary to improve the conventional vertical filling and packaging machine in order that the three-side seal type or the four-side seal type packaging bag with content may have high airtightness.
Here will be described with reference to FIG. 3 the reason why the lateral seal part of the three-side seal type or the four-side seal type packaging bag with content is wrinkled in the conventional vertical filling and packaging machine. FIG. 3 is a schematic view of a cylindrical film fed in a vertical direction when viewed from an upper side of a packaging machine.
For example, when the four-side seal type packaging bag is manufactured by using a conventional vertical filling and packaging machine, after forming cylindrical film 1 by folding a sheet-like film to overlap both sides thereof by a bag-making guide, heat-sealing in a longitudinal direction is carried out on the side of a folding part and the side of an overlapping part of cylindrical film 1. At this time, since it is difficult to completely make the peripheral lengths of surface A equal that of surface B of the film between vertical seal parts 8, strictly speaking, the peripheral lengths of the film surfaces between vertical seal parts 8 slightly differ in front surface A and back surface B as shown in FIG. 3. In addition, since the tip of injection pipe 7 is located right above ironing rollers 5 in cylindrical film 1 in a conventional vertical filling and packaging machine, a portion that is right above ironing rollers 5 of cylindrical film 1 is cylindrically swollen due to injection pipe 7 when the space between ironing rollers 5 is closed.
When cylindrical film 1 that is cylindrically swollen as described above is sandwiched between ironing rollers 5, cylindrical film 1 becomes easily wrinkled in the process of being crushed into a flat shape from the cylindrical shape. In addition, when the peripheral lengths of surface A and surface B between vertical seal parts 8 are different from each other in a state where cylindrical film 1 is cylindrically swollen, the width of the film is restricted by the film surface with the shorter peripheral length in the sandwiching process of cylindrical film 1 in which cylindrical film 1 is sandwiched between ironing rollers 5, and the film surface with the longer peripheral length becomes wrinkled (refer to FIG. 3(c)). The larger the diameter of injection pipe 7, the greater is cylindrical film 1 crushed from a cylindrically swollen state by ironing rollers 5, and thus cylindrical film 1 becomes easily wrinkled. Particularly, when a solid injecting pipe is used as in the two parts filling, it has been difficult to suppress formation of wrinkles since a pipe diameter of the solid injecting pipe is larger than that of a liquid injecting pipe.
In addition, since the vertical seal part is formed only on one side of cylindrical film 1 when the three-side seal type packaging bag is manufactured by using a conventional vertical filling and packaging machine, the films overlapping the other sides are easily misaligned when sandwiched between guide rollers 4. Hence, cylindrical film 1 may become wrinkled at the time when the sandwiching operation of ironing rollers 5 is performed.
In addition, the greater the amount of a product or the heavier the product, which is injected into longitudinally hung cylindrical film 1, the more easily is sag (the wavy portion) formed on surface A and surface B of cylindrical film 1. When cylindrical film 1 is sandwiched between ironing rollers 5 in this state, the wavy portion is crushed, as is, so that it becomes wrinkled.
Due to the above causes, the lateral seal part is formed while wrinkles remain in the packaging bag, such as the three-side seal type and the four-side seal type packaging bags.